Fiber-reinforced composite rods have been employed in a wide variety of applications as lightweight structural reinforcements. For example, power umbilicals are often used in the transmission of fluids and/or electric signals between the sea surface and equipment located on the sea bed. Such umbilicals generally include one or more pipes and electric conductors/wires collected in a bundle, a filler material arranged at least partly around and between the pipes and conductors/wires, and a protective sheath enclosing the pipes, conductors/wires, and filler material. To help strengthen such umbilicals, attempts have been made to use pultruded carbon fiber rods as separate load carrying elements. A significant problem with such rods however, it is that they rely upon thermoset resins (e.g., vinyl esters) to help achieve the desired strength properties. Thermoset resins are difficult to use during manufacturing and do not possess good bonding characteristics for forming layers with other materials. Attempts have been made to form rods from thermoplastic polymers in other types of applications. U.S. Patent Publication No. 2005/0186410 to Bryant, et al., for instance, describes attempts that were made to embed carbon fibers into a thermoplastic resin to form a composite core of an electrical transmission cable. Unfortunately, Bryant, et al. notes that these cores exhibited flaws and dry spots due to inadequate wetting of the fibers, which resulted in poor durability and strength. Another problem with such cores is that the thermoplastic resins could not operate at a high temperature.
As such, a need currently exists for a fiber-reinforced rod that is formed from a thermoplastic material, and yet is still capable of achieving the desired strength, durability, and temperature performance demanded by a particular application.